Patent GB-1366991-A (GB)
Title: Semiconductor device manufacture
IPC: H01L23/29
Filed: 1972-01-05
Abstract: 1366991 Semi-conductor devices PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 5 Jan 1972 [8 Jan 1971] 509/72 Heading H1K A semi-conductor device comprises (Fig. 9) a planar Si semi-conductor body formed with an IGFET together with other components in a monolithic integrated circuit; with a P-type substrate 1 having N-type source and drain zones; and a surface insulating SiO 2  layer 2, 6 overlain by Al gate 12 and electrodes 10, 11 In manufacture, the substrate is etched and polished, and coated with SiO 2  by thermal moist oxidation, and the coating is apertured, by etching over photoresist, for in-diffusion of P from POCl 3  to form N-type source and drain zones 4, 5 (Figs. 1, 2, 3, not shown). The layer is removed at the gate zone by masking and etching and a thin oxide layer 6 is thermally formed in moist O 2 . The oxide on the underside of the substrate is removed and replaced by a gettering phosphosilicate glass layer 7 also extending over the oxide layer, which forms a N-type layer 9 on the underside (Fig. 6). It is removed from the oxide layer 2, 6 by etching with dilute HF + H + NO 3  (Fig. 7, not shown); the layer in the underside being masked. A phosphorus in-diffusion at low surface concentration is effected thermally in N 2  + O 2  + POCl 3  to stabilize and passivate the oxide layer below the gate electrode (Fig. 8, not shown) and impurities, e.g. Au, or Cu in the Si and Na in the S<SP>1</SP>O 2 , which cause instability, leakage, and breakdown are removed as a final step by heating the plate to high temperature so that the phosphosilicate glass layer 7 exerts a gettering effect and extends the in-diffusion of layer 9. Etched windows in the oxide layers 2, 6 admit gate, source, and drain electrodes 12, 10, 11 formed by known masking and vapour deposition. Borosilicate glass is usable for gettering, and the insulant layer may be Si 3 N 4  or Al 2 O 3  or composites thereof. The substrate may be of Ge or an A III B V  compound, and Si 3 N 4  is usable to passivate the oxide. The process may be applied to fabrication of a camera tube target comprising N-type Si plate 21, B diffused to form P zones 22 of plural diodes; the plate being covered with insulant SiO 2  at 23 and apertured to expose the diodes. Incident light 24 charges the diodes to levels dependent on incumbent radiation, and the opposite side of the plate is scanned by an electron beam cyclically neutralizing the diodes, so that electron flow through contact 25 establishes current variations, (Fig. 14). In formation, the oxide layer is removed from the underside of the plate (Fig. 10, not shown) and the body is covered with phosphosilicate glass 27 (Fig. 11, not shown) forming a thin highly doped N layer 28 on the underside of the plate. The phosphosilicate glass layer is removed from the upper side (Fig. 12) by etching and the plate is gettered at high temperature in-diffusing the phosphorus. The thin oxide layer covering the zones is etched off in buffered HF leaving sufficient oxide between the diodes and windows 26. The plate is etched down on the lower side and annular contact 25 is applied. Zones 22 may be N-type and plate 21 P-type for a positive charge scanning beam.